This invention relates generally to improvements in automotive hoists or the like. More specifically, the invention relates to an improved safety latch apparatus for automotive hoists.
Numerous approaches have been taken to design safety latches for automotive hoists or lifts. Three of these are illustrated in U.S. Pat. No. 2,059,059 issued to E. B. Thompson on Oct. 27, 1936, U.S. Pat. No. 2,750,004 issued to J. B. Harrison on June 12, 1956, and U.S. Pat. No. 2,849,084 issued to I. V. K. Hott et al on Aug. 26, 1958.
In addition to the above, it has also been relatively common practice to equip the hoist with a tubular member that is attached to the piston of the hoist and thus rises therewith. The tube telescopes within a cylinder or sleeve that is mounted in the ground. Upon reaching the full upper position of the hoist, a pin is simply inserted through the cylinder and the tube to prevent the telescoping of the tube within the cylinder until the pin is removed.
Another approach to the design of safety latches for hoists has been to provide a tube that is hinged on the piston so that it rises with the piston. Upon reaching the uppermost position of the hoist, the tube is pivoted downwardly engaging the surface of the ground to prevent inadvertent downward movement of the hoist.
Each of the foregoing described latches will operate to prevent accidental downward movement of the hoist. Some of the latches are rather complex, resulting in maintenance difficulty and increased cost.
As those skilled in the art will appreciate, some of the prior art latches have the disadvantage of locking only when the hoist is in its uppermost position and, should a failure occur during raising of the hoist, the latch is inoperative. However, some of the aforementioned latches can be utilized at intermediate positions of the hoist, but most must be engaged manually at such intermediate positions.
The improved latch apparatus of this invention is operative during the raising of the hoist and is, in fact, biased into latching engagement by the act of raising the hoist so that no matter when the failure of the hoist power system occurs the latch will immediately engage to prevent downward movement of the hoist.
Further, the improved latch of this invention is relatively simple, thereby reducing maintenance and manufacturing costs.